What is the best way to approach fixing illegal conversions?

[Bin Chen]

I hear the DOB is getting more strict in terms of illegal conversions but I see so many listings for houses that have obviously been illegally converted. I hear the fines are 15k per unit. There are so many listings that go something along the line of "2 family house set up with 3 units" or "3 family house" but the 3rd unit is in the cellar when you check the c/o online it says its a 2 family house. From my point of view there is so much risk to something like that. If there is a fire or something happens to the cellar tenant, I'm sure the insurance company will void your insurance stating the house was not used as intended. The tenants can basically black mail you by threatening to report you to the DOB. 

I don't want want to deal with that so I was wondering how to approach removing an existing tenant from an illegal unit. If you go through the eviction process will you be fined by the DOB for renting an illegal unit in the first place? I guess if you can prove you bought it like that then the fine won't go to you right? Has anyone dealt with this before?